go.tools/cmd/stringer: fix docs: stringer is not a "go tool" Documentation change only. The binary will not be installed using the "go tool" mechanism.
go.tools/cmd/stringer: fix docs: stringer is not a "go tool"
Documentation change only. The binary will not be installed
using the "go tool" mechanism.

LGTM=gri
R=gri
CC=golang-codereviews
https://codereview.appspot.com/133710046

d0f/go-zh.tools,bryanxu/go-zh.tools,d0f/go-zh.tools,webfd/go-zh.tools,webfd/go-zh.tools,d0f/go-zh.tools,webfd/go-zh.tools,webfd/go-zh.tools,d0f/go-zh.tools,bryanxu/go-zh.tools,bryanxu/go-zh.tools,d0f/go-zh.tools,bryanxu/go-zh.tools,webfd/go-zh.tools,bryanxu/go-zh.tools